DISTRIBUTION OF GLUTAMINE-SYNTHETASE IN THE SNAPPER (PAGRUS-AURATUS) AND IMPLICATIONS FOR THE IMMUNE-SYSTEM

A sensitive radiotracer method was used to detect glutamine synthetase activity in fish. The distribution of glutamine synthetase activity u sing this method was shown to be widespread in organs and tissues of t he marine finfish, snapper, Pagrus auratus. The optimum pH and tempera ture for glutamine synthetase activity and Km Of glutamate from the br ain of the snapper are also reported. Interestingly no glutamine synth etase activity was detected in lymphoid organs, indicating, that as in the mammal, the teleostean immune system is likely to rely on glutami ne in circulation for energy and nucleotide synthesis. Furthermore cir culating glutamine levels fell as fish became stressed or became ill. Implications of these observations on the function of the immune syste m of fish are discussed.